Californians have fundamentally altered many of the state’s rivers and streams with dams, pipes, and diversions, and the State is home to some of the world’s most complex water delivery projects. As an unfortunate consequence, habitat for many freshwater species has been degraded or destroyed.

But, is it necessary to tradeoff the freshwater needs of birds, fish, and other species against the needs of farms and cities? Could freshwater flows be managed to better mimic the dynamics of their unimpaired past, dynamics to which native species have adapted and need to persist? And how should climate change considerations be incorporated into water management, to enhance the resilience of freshwater systems for both people and nature?

Our science is focused on tackling these questions.

Science in Action

Freshwater | Science

Restoring California’s Largest River

How can we restore large rivers and floodplains to benefit nature and people?

Freshwater | Terrestrial | Science

Not Leaving it to Beaver

Can we restore meadows by mimicking beavers?

2021 | Freshwater | Science | Maps & Webmaps

California Natural Flows Webapp

Julie K.H. Zimmerman, Daren M. Carlisle, Jason T. May, Kirk R. Klausmeyer, Theodore E. Grantham, Larry R. Brown, Jeanette K. Howard, Nathaniel Rindlaub, Falk Schuetzenmeister

Water is essential for California’s people, economy, and environment. Centuries of water management through dams and diversion have altered the flows in many streams and rivers, which can harm…

2021 | Freshwater | Planning | Maps & Webmaps

ICONS: Interconnected Surface Water in the Central Valley

Charlotte Stanley, Kirk Klausmeyer

This dataset categorizes the rivers and streams in the Central Valley on the likelihood that they are interconnected surface water (ISW) -- surface water hydraulically connected to groundwater. The…

2020 | Freshwater | Science | Publications & Reports

Evaluating and Protecting Environmental Water Assets: A Guide for Land Conservation Practitioners

Author: Chris Alford, Editors and Reviewers: Amy Campbell, Monty Schmitt, Sara Press, Wendy Eliot, Bob Neale

Evaluating and Protecting Environmental Water Assets: A Guide for Land Conservation Practitioners, a publication by TNC and the Sonoma Land Trust (SLT), provides provides easy to understand guidance,…

2020 | Freshwater | Marine | Science | Microsite

State of Salmon in California

Sally Liu, Megan Webb, Jeanette Howard, Jennifer Carah

Chinook, coho and steelhead were once tremendously abundant in most of California’s major rivers and streams. As recently as the 1960s, salmon and steelhead were so plentiful in streams that…

2020 | Freshwater | Science | Publications & Reports

A functional flows approach to selecting ecologically relevant flow metrics for environmental flow applications

Sarah M. Yarnell, Eric D. Stein, J. Angus Webb, Theodore Grantham, Rob A. Lusardi, Julie Zimmerman, Ryan A. Peek, Belize A. Lane, Jeanette Howard, Samuel Sandoval-Solis

The authors of this paper are engaged in developing flow criteria for California Streams through California Environmental Flows Framework (CEFF) collaboration. The effort is funded by the State…

2019 | Freshwater | Planning | Science | Publications & Reports

Dynamic multibenefit solutions for global water challenges

Melissa M. Rohde, Mark Reynolds, Jeanette Howard

In this article, the authors provide an example of how dynamic multi-benefit solutions used to provide “pop-up” wetland habitat for migratory birds also replenishing depleted aquifers to…

2019 | Freshwater | Science | Publications & Reports

Cannabis and residential groundwater pumping impacts on streamflow and ecosystems in Northern California

Samuel C. Zipper, Jennifer K. Carah, Christopher Dillis, Tom Gleeson, Ben Kerr, Melissa M. Rohde, Jeanette K. Howard, Julie K.H. Zimmerman

Using a newly developed tool for estimating streamflow depletion from groundwater pumping, this study examined the impacts of ongoing groundwater pumping on streamflow and aquatic ecosystems in the…

2019 | Freshwater | Terrestrial | Science | Publications & Reports

First known survey of cannabis production practices in California

Houston Wilson, Hekia Bodwitch, Jennifer Carah, Kent Daane, Christy Getz, Theodore E. Grantham, Van Butsic

Cannabis has been an industry in the shadows for many decades and little studied. In partnership with U.C. Berkeley and U.C. Cooperative Extension, the Conservancy staff developed the first cannabis…

2019 | Freshwater | Science | Publications & Reports

Rapid and Accurate Estimates of Streamflow Depletion Caused by Groundwater Pumping Using Analytical Depletion Functions

Samuel C. Zipper, Tom Gleeson, Ben Kerr, Jeanette K. Howard, Melissa M. Rohde, Jennifer Carah, Julie Zimmerman

Reductions in streamflow from groundwater pumping can negatively impact water users and aquatic ecosystems but are challenging to estimate due to the time and expertise required to develop numerical…

2019 | Freshwater | Planning | Science | Publications & Reports

Conservation Planning Foundation for Restoring Chinook Salmon (Oncorhynchus tshawytscha) and O. mykiss in the Stanislaus River

Prepared by Anchor QEA, LLC (John Ferguson, Elizabeth Greene, and Michelle L. Ratliff), Contributors and Participants: John Cain, Jon Rosenfield, Alison Weber-Stover, Stephen Louie, John Shelton, Tim Heyne, Brian Ellrott, Sierra Franks, Monica Gutierrez, Rhonda Reed, David Swank, Steve Edmundson, Katie Schmidt, Rachel Johnson, Jeanette Howard, Julie Zimmerman, Chris Carr, Daniel Worth, Rene Henery, Ron Yoshiyama, Joshua Israel, Paul Cadrett, Ramon Martin, and J.D. Wikert

Also view Appendix A: Stanislaus Survival Model and and other report Appendices.  

2019 | Freshwater | Terrestrial | Science | Publications & Reports

Clarifying Effects of Environmental Protections on Freshwater Flows to—and Water Exports from—the San Francisco Bay Estuary

Gregory J. Reis, Jeanette K. Howard, Jonathan A. Rosenfield

For years the narrative of the San Francisco Bay Delta has been driven by the contention that water use by agriculture was being limited by environmental regulation. Analyzing long-term trends…

2019 | Freshwater | Science | Publications & Reports

Stream flow modeling tools inform environmental water policy in California

Theodore E. Grantham, Julie K. H. Zimmerman, Jennifer K. Carah, Jeanette K. Howard

Management of California’s vast water distribution network, involving hundreds of dams and diversions from rivers and streams, provides water to 40 million people and supports a globally…

2018 | Freshwater | Terrestrial | Science | Blogs

The Promise of eDNA: A New Kind of Fieldwork to Guide Conservation

Sophie Parker

This blog post discusses how environmental DNA or “eDNA” methods can be used by conservation biologists. These methods rely on the premise that DNA is shed by organisms through normal,…

2018 | Freshwater | Planning | Science | Maps & Webmaps

Rearing habitat objectives to support salmon in the Central Valley

Travis M. Hinkelman, Myfanwy Johnston, Joseph E. Merz, Julie Zimmerman

To restore degraded stream corridors and develop large-scale, sustainable watershed conservation strategies, it is essential for managers to consider—in order to ultimately…

2018 | Freshwater | Terrestrial | Planning | Science | Publications & Reports

Water Supply and Habitat Resiliency for a Future Los Angeles River: Site-Specific Natural Enhancement Opportunities Informed by River Flow and Watershed-Wide Action

Brian Cohen, Shona Ganguly, Sophie Parker, John Randall, Jill Sourial, and Lara Weatherly of The Nature Conservancy, Land IQ, Natural History Museum Los Angeles County, WRC Consulting Services Inc., Travis Longcore, University of Southern California, Connective Issue, Inc.

As a basic principle of ecological systems, a watershed’s hydrology determines the flow characteristics of its river system. These flows define what the biological characteristics of that…

2018 | Freshwater | Terrestrial | Planning | Science | Publications & Reports

Ecological Values of the Amargosa River in California

Sophie S. Parker, Jim Moore, Leonard Warren

The 185 mile-long Amargosa River, one of only two rivers with perennial flow in the California portion of the Mojave Desert, is fed by an ancient groundwater aquifer. The river provides habitat for…

2018 | Freshwater | Terrestrial | Marine | Planning | Science | Publications & Reports

Improving multi-objective ecological flow management with flexible priorities and turn-taking: a case study from the Sacramento River and Sacramento-San Joaquin Delta

Alexander C.A.D., F. Poulsen, D.C.E. Robinson, B.O. Ma , R.A. Luster

Management of the Sacramento River and Sacramento–San Joaquin Delta is one of California’s greatest challenges, requiring trade-offs between valued components that serve a multiplicity of…

2018 | Freshwater | Terrestrial | Science | Publications & Reports

Using ricelands to provide temporary shorebird habitat during migration

Gregory H. Golet, Candace Low, Simon Avery, Katie Andrews, Christopher J. McColl, Rheyna Laney, Mark D. Reynolds

Migratory birds face great challenges due to the climate change, conversion of historical stopover sites, and other factors. To help address these challenges, the Conservancy launched a dynamic…